Swimming pools, Jacuzzis, and spas (hereinafter collectively referred to as "swimming pools" or "pools " unless specifically indicated otherwise) contain significant amounts of water, which, relative to the environment outside of the pools, is stagnant, but exposed to the environment. Furthermore, in the normal use of the pools, users bring into the pools any number of bacteria. Therefore, over a period of time, if not disinfected in some way, the bacterial count of the pool water would make the pools unsuitable for use. This is especially problematical in pools in which the water is slightly heated. As such, pool disinfectants have been developed and used to keep the pool bacterial level well below the maximum acceptable level.
Unfortunately, many of these products result in unacceptably low pH, causing pool user irritation as well as pool wall, floor, and water-recirculation/filtration system pitting and erosion. In addition, in many areas, acid rain shifts the pH of the pools to unacceptably low levels causing the same problems.
In response to these difficulties, alkalinizing agents have been added to the pool water after disinfection has been completed. Typically, the alkalinizing agent has been sodium carbonate or sodium bicarbonate or sodium sesquicarbonate, and the material has been spread in the pool by broadcasting it across the surface of the pool.
Difficulties in this procedure include the problem that sodium bicarbonate alone does not raise the pH sufficiently, while the amount of sodium carbonate that would raise the pH appropriately without unacceptably overshooting the desired pH is small and hard to control. In addition, these compounds are fairly dusty and broadcasting them across the pool surface, to enhance efficient dispersion, frequently results in surrounding areas being dusted as well. This means that surrounding foliage frequently gets dusted with highly alkaline materials, a dusting which is known to be phytotoxic. Also, the dissolution rate is slow which can result in the pool being closed for hours. Furthermore, the alkali resting on the pool floors can cause staining, especially of colored tile.
Difficulties also arise with sodium sesquicarbonate as the alkalinizer. While this compound is a composite of both carbonate and bicarbonate, it also dissolves slowly. Therefore, it frequently sinks to the bottom of the pool and does not effectively disperse. Therefore, there is a very local area that has had its pH adjusted, while the remainder of the water does not receive appropriate alkalinization for a very extended time.
As can be readily seen, in each instance, there is an extremely large margin for error in the pH adjustment of the water, requiring adjustment, checking, back adjusting for any pH overshoot, rechecking the pH and repeating the process until a pH within appropriate limits is achieved.
A further problem with the use of the currently used commercial methods is that there is a large lag time between placing the chemicals into the pool water and when one can check the pH reasonably accurately. Checking the pH too quickly will result in a false reading, either too low or too high, depending on which pH adjustment direction was last attempted. This is so because the amount of chemicals added is relatively small compared to the total pool volume and the mixing of the chemicals in the pool water is not very efficient. Hence, one typically has to wait on the order of a pool turnover of at least three times in order to be reasonably confident that the measured pH is within acceptable limits of the pH in the pool at large. This time frame is even longer where the material is not as soluble, since a significant portion of the alkalinizer may not even be in solution when one attempts to measure the pH and base an adjustment on such measurement.